4.4-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit e1f65b0d70e9e5c80e15105cd96fa00174d7c436 ]
It seems with some NICs supported by the e1000e driver a SYSTIM reading may occasionally be few microseconds before the previous reading and if enabled also pass e1000e_sanitize_systim() without reaching the maximum number of rereads, even if the function is modified to check three consecutive readings (i.e. it doesn't look like a double read error). This causes an underflow in the timecounter and the PHC time jumps hours ahead.
This was observed on 82574, I217 and I219. The fastest way to reproduce it is to run a program that continuously calls the PTP_SYS_OFFSET ioctl on the PHC.
Modify e1000e_phc_gettime() to use timecounter_cyc2time() instead of timecounter_read() in order to allow non-monotonic SYSTIM readings and prevent the PHC from jumping.
Cc: Richard Cochran richardcochran@gmail.com Signed-off-by: Miroslav Lichvar mlichvar@redhat.com Acked-by: Jacob Keller jacob.e.keller@intel.com Tested-by: Aaron Brown aaron.f.brown@intel.com Signed-off-by: Jeff Kirsher jeffrey.t.kirsher@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/intel/e1000e/ptp.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/intel/e1000e/ptp.c b/drivers/net/ethernet/intel/e1000e/ptp.c index 25a0ad5102d6..855cf8c15c8a 100644 --- a/drivers/net/ethernet/intel/e1000e/ptp.c +++ b/drivers/net/ethernet/intel/e1000e/ptp.c @@ -111,10 +111,14 @@ static int e1000e_phc_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts) struct e1000_adapter *adapter = container_of(ptp, struct e1000_adapter, ptp_clock_info); unsigned long flags; - u64 ns; + u64 cycles, ns;
spin_lock_irqsave(&adapter->systim_lock, flags); - ns = timecounter_read(&adapter->tc); + + /* Use timecounter_cyc2time() to allow non-monotonic SYSTIM readings */ + cycles = adapter->cc.read(&adapter->cc); + ns = timecounter_cyc2time(&adapter->tc, cycles); + spin_unlock_irqrestore(&adapter->systim_lock, flags);
*ts = ns_to_timespec64(ns); @@ -170,9 +174,12 @@ static void e1000e_systim_overflow_work(struct work_struct *work) systim_overflow_work.work); struct e1000_hw *hw = &adapter->hw; struct timespec64 ts; + u64 ns;
- adapter->ptp_clock_info.gettime64(&adapter->ptp_clock_info, &ts); + /* Update the timecounter */ + ns = timecounter_read(&adapter->tc);
+ ts = ns_to_timespec64(ns); e_dbg("SYSTIM overflow check at %lld.%09lu\n", (long long) ts.tv_sec, ts.tv_nsec);